Mounting multiple semiconductor dies in a package

ABSTRACT

A semiconductor device includes multiple dies, in which a first die and a second die are mounted on a leadframe. The bond pads on the first and second dies are wirebonded to the leadframe. The first die, second die, and leadframe are encapsulated in a package.

BACKGROUND

[0001] The invention relates to mounting multiple semiconductor dies ina package.

[0002] A typical semiconductor device starts with a single die that issawed from a silicon wafer. Circuitry is formed on the die by a seriesof deposition, masking, diffusion, etching, and implanting steps. Theback of the die is bare. The die is attached to the leadframe by anadhesive layer that can also serve to electrically insulate the die fromthe leadframe. The die is then electrically connected to the leadframeby wirebonding the lead fingers of the leadframe to a bonding padsdisposed around the periphery of the die (conventional configuration),or down the center of the die in a lead-on-chip (LOC configuration).After wirebonding, the die and the leadframe are encapsulated in amolded plastic package that is hermetically sealed to protect the diefrom moisture and physical stress. The lead fingers extend outside theplastic package to form leads that are folded down the side of theplastic package.

[0003] Various methods have been developed to increase package density.For example, U.S. Pat. No. 5,012,323, having the same assignee as thepresent application, discloses a semiconductor package incorporating apair of conventional semiconductor dies (a first die mounted over asecond die) on a single leadframe. The bonding pads on a conventionaldie are located on its periphery. To enable the bonding pads of thesecond die to be wirebonded to the leadframe, the rectangular surfacearea of the first die (mounted over the second die) is shown as beingsmaller than that of the second die.

SUMMARY

[0004] In accordance with one aspect of the present invention, amultiple die package includes a pair of dies having bonding pads andfront surfaces on which the bonding pads are located, the front surfacesfacing oppositely from one another. The package also includes aleadframe. One of the dies is secured on the leadframe. A bond pad ofthat die is electrically connected to the leadframe.

[0005] In accordance with another aspect of the present invention, amultiple die package includes a pair of dies having bonding pads andfront surfaces on which the bonding pads are located, the front surfacesfacing in the same direction. The package also includes a leadframe. Atleast one of the dies is secured to the leadframe. A spacer is used forspacing the dies from one another.

[0006] In accordance with yet aspect of the present invention, a methodinvolves mounting multiple semiconductor dies on a single leadframe bystacking at least two semiconductor dies having about the samerectangular dimensions on top of one another. The stacked dies areelectrically connected to the leadframe.

[0007] In accordance with but another aspect of the present invention, amethod of connecting multiple semiconductor dies having bonding pads anda single leadframe having lead fingers includes mounting a firstsemiconductor die on the lead fingers of the leadframe. A secondsemiconductor die is stacked on the first semiconductor die. The bondingpads of the semiconductor dies are electrically connected to the leadfingers of the leadframe.

[0008] In accordance with another aspect of the present invention, asemiconductor device includes a plurality of semiconductor dies havingabout the same rectangular dimensions. A leadframe has lead fingers towhich the semiconductor dies are mounted. Connectors electricallyconnect the dies to the leadframe.

[0009] In accordance with yet another aspect of the present invention, asemiconductor device has a leadframe with a first surface, a secondsurface opposite the first surface, and lead fingers. A first die islocated on the first surface, the first die having bond pads which areelectrically contacted to the lead fingers on the first surface of theleadframe. A second die is located on the second surface, the second diehaving bond pads which are electrically contacted to the lead fingers onthe second surface of the leadframe.

[0010] In accordance with but another aspect of the present invention,an integrated circuit package has a leadframe with first and secondsurfaces. A support member is mounted to a first surface of theleadframe. A first die is mounted to the support member, and a seconddie is mounted to a second surface of the leadframe.

[0011] Advantages of the invention include one or more of the following:a higher density integrated circuit device, multiple dies having thesame size may be mounted on a single leadframe, and a semiconductorpackage having both LOC and conventional dies. Other advantages willbecome apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an enlarged, cross-sectional view of a semiconductordevice having first and second dies mounted on a leadframe.

[0013]FIG. 2 is an enlarged, cross-sectional view of a semiconductordevice having first and second dies mounted underneath a leadframe.

[0014]FIG. 3 is an enlarged, cross-sectional view of a semiconductordevice having first die mounted on top of a leadframe and a second diemounted underneath the leadframe.

[0015]FIG. 4 is an enlarged, cross-sectional view of a semiconductordevice having first die mounted on a support frame that is mounted ontop of a leadframe and a second die mounted underneath the leadframe.

[0016]FIG. 5 is an enlarged, cross-sectional view of a semiconductordevice having first die mounted under an offset portion of a leadframeand a second die mounted on the leadframe under and spaced apart fromthe first die.

[0017]FIG. 6 is an enlarged, cross-sectional view of a semiconductordevice having first die mounted on top of an offset portion of aleadframe and a second die mounted underneath the leadframe.

DETAILED DESCRIPTION

[0018] Referring to FIG. 1, a semiconductor package 10A includes a firstsemiconductor die 20 and a second semiconductor die 30 stacked one ontop of the other, and a leadframe 170 encapsulated by a package body 11.The package body 11 hermetically seals the first die 20, second die 30and the leadframe 170 to protect the dies 20, 30 and the leadframe 170from moisture and physical stress and mechanical damage. The packagebody 11 may be made of, for example, plastic, ceramic, or other hard anddurable material, and may be a dual inline package (DIP), small outlineJ-lead package (SOJ), thin small outline package (TSOP), or any othertype package.

[0019] The first die 20, which may have an LOC configuration, is mountedface down on the leadframe 170, with its face 21 adjacent a top surface173 of the leadframe 170. The die 20 may be adhered to the leadframe 170by an adhesive layer 160. The second die 30, which has a conventionalconfiguration, is mounted face up on the first die 20, with its back 32adjacent the back 22 of the first die 20, and adhered to the first die20 by the adhesive layer 160. The adhesive layer 160 may be anonconductive double adhesive tape such as the type conventionally usedin LOC packages. Alternatively, a conductive adhesive layer can be usedif a common electrical connection between the two die is required suchas ground.

[0020] The leadframe 170 may be made of metal, for example, Alloy-42,and has leads 171 and lead fingers 172. The lead fingers 172 areencapsulated within the package body 11 and extend towards a center ofthe package body 11. The leads 171 extend outside the package body 11and may be formed into through-holes, J-leads, gull wings, or othervariations thereof. To facilitate soldering of leads 171 to aninterconnecting structure, leads 171 may be tin plated or solder dipped.

[0021] One advantage of the semiconductor device 10A is that multipledies may be conveniently encapsulated in a single package body. Anotheradvantage of is that the multiple dies may have the same or may not havethe same rectangular dimensions, even though both are shown as havingthe same dimensions in FIG. 1.

[0022] Referring to FIG. 2, a semiconductor package 10B includes a firstLOC die 20 and the second conventional die 30 stacked one on top of theother. The face 21 of the first die 20 is oriented upwardly and ismounted to a bottom surface 174 of the leadframe 170. The face 31 of theother die 30 is directed away from the die 20. Otherwise, theembodiments shown in FIGS. 1 and 2 are the same.

[0023] A semiconductor package 10C, shown in FIG. 3, includes a firstconventional die 40, a second conventional die 50, and a leadframe 170encapsulated within the package body 11. A back 42 of the first die 40is mounted on the bottom surface 174 of the leadframe 170 by theadhesive layer 160. The back 52 of the second die 50 is mounted to thetop surface 173 of the leadframe 170 and adhered to leadframe 170 byanother adhesive layer 160. Thus, the dies 40 and 50 face oppositelyfrom one another. The first die 40 and second die 50 have a plurality ofbonding pads 43 and 53 disposed along the periphery of their face 41 and51. Bonding wires 44 and 54 of the dies 40 and 50 electrically connectbonding pads 43 and 53 to the lead fingers 172.

[0024] Referring now to FIG. 4, a semiconductor package 10D includes afirst LOC die 60 mounted to the leadframe 170 with its face 61 adjacentthe bottom surface 174 of the leadframe 170. A rectangular spacer 150 isattached to the top surface 173 of the leadframe 170 by an adhesivelayer 161. This spacer can be in the form of two single strips or awindow frame shape. The back 72 of a second conventional die 70 ismounted to the spacer 150 and adhered to the support frame 150 by theadhesive layer 160. The spacer 150, which may be made of a nonconductivematerial such as plastic, spaces the die 70 from the leadframe 170 andallows the dies 60 and 70 to face in the same direction.

[0025] The first die 60 has a plurality of bonding pads 63 disposed onits face 61 generally down the center of the die 60. The second die 70has a plurality of bonding pads 73 disposed on its face 71 along theperiphery. A plurality of bonding wires 64 and 74 electrically connectthe bonding pads 63 and 73 to the lead fingers 172.

[0026] Referring now to FIG. 5, a semiconductor package 10E has apackage body 11 that encapsulates a first upwardly facing LOC die 80, asecond downwardly facing conventional die 90, and a leadframe 180. Theleadframe 180 has leads 181 and lead fingers 182. Additionally, theleadframe 180 has an offset portion 184 formed in the lead fingers 182.The first die 80 is mounted to the leadframe 180 with its face 81adjacent a bottom surface 185 of the offset portion 184, adhered toleadframe 180 by the adhesive layer 160. The second die 90 is mounted toleadframe 180 with its back 92 adjacent the bottom surface 185 of theupset portion 184 spaced apart from first die 80. The die 90 is adheredto the leadframe 180 by the adhesive layer 160.

[0027] The first die 80 has a plurality of bonding pads 83 disposed onits face 81 generally down the center. The second die 90 has a pluralityof bonding pads 93 disposed on its face 91 along the periphery. Thebonding pads 83 and 93 are connected to the lead fingers 182 by bondingwires 84 and 94 respectively.

[0028] Because of the smaller surface area of the offset portion 184 ofthe leadframe 180 as compared to the lead fingers 172 of the leadframe170, the first die 80 and the second die 90 need not have the samerectangular dimensions. The offset 184 allows each back to back die 80and 90 to be conveniently contacted.

[0029] It is not necessary that the two dies use the same leads, asshown in FIG. 5, for illustration purposes only. Alternatively, theoffset portion 184 may be downwardly rather than upwardly directed andthe die mounted on top of the leadframe 120 rather than under it.

[0030] Referring now to FIG. 6, a semiconductor package 10F includes afirst downwardly facing LOC die 100, a second downwardly facingconventional die 90, and a leadframe 180. The package 10F in FIG. 6 isthe same as the package 10E in FIG. 5 except for the first die 100,which may be the same size as the die 90. The first die 100 is mountedto the leadframe 180 with its face 101 adjacent a top surface 186 of theoffset portion 184, and adhered to leadframe 180 by the adhesive layer160. Bonding pads 103 are disposed on the face 101 of the first die 100generally down the center of the first die 100. Bonding wires 104electrically connect the bonding pads 103 to the lead fingers 182.Alternatively, the offset 184 may be downwardly directed instead ofupwardly directed so that the die 100 is on the bottom and the die 90 ison the top.

[0031] It is to be understood that the embodiments described above aremerely illustrative of some of the many specific embodiments of theinvention, and that other arrangements can be devised by one of ordinaryskill in art at the time the invention was made without departing fromthe scope of the invention. For example, although FIGS. 1-6 illustratepackages with two dies, more dies may be mounted on a single leadframe.

[0032] What is claimed is:

1. A multiple die package comprising: a pair of dies having bonding padsand front surfaces on which said bonding pads are located, said frontsurfaces facing oppositely from one another; and a leadframe, at leastone of said dies secured on said leadframe and with a bonding pad of oneof said dies electrically connected to said leadframe.
 2. The package ofclaim 1 , wherein said dies are stacked one on top of the other.
 3. Thepackage of claim 2 , wherein said leadframe is secured to one of saiddies.
 4. The package of claim 2 , wherein each of said dies includes aback surface opposite to said front surface, said back surface of eachof side dies connected to one another.
 5. The package of claim 2 ,wherein each of said dies includes a back surface opposite to said frontsurface, said back surface of each die facing one another, each of saidback surfaces connected to said leadframe.
 6. The package of claim 2 ,wherein each of said dies are secured to said leadframe.
 7. The packageof claim 6 , wherein each of said dies are secured to said leadframe ata different location.
 8. The package of claim 6 , wherein leadframeincludes an offset.
 9. The package of claim 8 , wherein each of saiddies is connected to the same side of said leadframe.
 10. The package ofclaim 8 , wherein each of said dies is connected to a different side ofsaid leadframe.
 11. A multiple die package comprising: a pair of dieshaving bonding pads and front surfaces on which said bonding pads arelocated, said front surfaces facing in the same direction; a leadframe,at least one of said dies secured to said leadframe; and a spacer forspacing said dies from one another.
 12. The package of claim 11 ,wherein said spacer is secured to said leadframe and one of said dies issecured to said spacer.
 13. The package of claim 11 , wherein saidspacer is integral with said leadframe.
 14. The package of claim 13 ,wherein said spacer is formed by an offset portion of said leadframe.15. A method for mounting multiple semiconductor dies on a singleleadframe, comprising: stacking at least two semiconductor dies havingsubstantially the same rectangular dimensions on top of one another; andelectrically connecting the semiconductor dies to the leadframe.
 16. Themethod of claim 15 , wherein a first semiconductor die is mounted backto back on a second semiconductor die.
 17. The method of claim 16 ,wherein the first semiconductor die is adhered to the secondsemiconductor die by an adhesive layer.
 18. The method of claim 15 ,wherein a first semiconductor die has a lead-on-chip configuration. 19.The method of claim 15 , wherein one of said dies is secured to saidleadframe and the other of said dies is secured to the die secured tothe leadframe.
 20. The method of claim 15 , further comprisingwirebonding the semiconductor dies to the leadframe, said dies havingfacing sides and outwardly facing sides by extending wires to bond padson the outwardly facing sides of said die.
 21. A method of connectingmultiple semiconductor dies having bonding pads and a single leadframehaving lead fingers, comprising: locating a first semiconductor die onthe lead fingers of the leadframe; stacking a second semiconductor dieon said first semiconductor die; and electrically connecting the bondingpads of the semiconductor dies to the lead fingers of the leadframe. 22.The method of claim 21 , further comprising encapsulating thesemiconductor dies and the leadframe in a single package body.
 23. Asemiconductor device, comprising: a plurality of semiconductor dieshaving about the same rectangular dimensions; a leadframe having leadfingers to which the semiconductor dies are mounted; and connectors forelectrically connecting the dies to the leadframe.
 24. The semiconductordevice of claim 23 , further comprising: a first semiconductor diemounted to a first side of the leadframe; and a second semiconductor diemounted to a second, different side of the leadframe.
 25. Thesemiconductor device of claim 23 , wherein the lead fingers have a firstportion and a second portion, further comprising: a first semiconductordie mounted on a first portion of the lead fingers; and a secondsemiconductor die mounted on a second, different portion of the leadfingers, wherein the second portion is offset from the first portion.26. The semiconductor device of claim 23 , further comprising: a supportmember mounted to a first side of the leadframe; a first semiconductordie mounted onto the support frame; and a second semiconductor diemounted to a second, different side of the leadframe.
 27. A package formultiple semiconductor dies, comprising: a plurality of semiconductordies stacked one on top of the other; a leadframe having lead fingers onwhich the semiconductor dies are mounted; and a package body forhermetically encapsulating the semiconductor dies and the leadframe. 28.A semiconductor device, comprising: a leadframe having a first surface,a second surface opposite said first surface, and lead fingers; a firstdie located on the first surface, the first die having bond pads whichare electrically contacted to the lead fingers on the first surface ofthe leadframe; and a second die located on the second surface, thesecond die having bond pads which are electrically contacted to the leadfingers on the second surface of the leadframe.
 29. An integratedcircuit package, comprising: a leadframe having first and secondsurfaces; a support member mounted to a first surface of the leadframe;a first die mounted to the support member; and a second die mounted to asecond surface of the leadframe.
 30. The integrated circuit package ofclaim 29 , wherein the support member is made of an electricallynon-conductive material.
 31. The integrated circuit package of claim 29, wherein each die has bond pads mounted on and a surface on which saidbond pads are mounted, said surfaces of each die facing in the samedirection.